When machining a metal work piece by means of a rotating milling disc, it is often advantageous or even necessary to flush the work piece and/or the milling disc with a flushing fluid in the form of a gas, liquid or a mixture of gas and liquid. Such flushing can be performed for different reasons, e.g. for cooling or lubricating or for washing away cuttings or chips from the work piece during machining.
The most common way to achieve flushing of a slot milling disc is to simply direct a stream of liquid and/or gas from the outside towards the milling disc and the work piece at an area where the actual machining takes place. A disadvantage with such a flushing method is that the flushing will be very ineffective as most of the fluid will not reach the area where it could be of use. In case of a liquid flushing medium, this has the result that there will be formed a large amount of waste liquid, which has to be collected and filtered or disposed of.
EP 1897642 discloses a milling tool in form of a so called gear milling cutter, which is formed of two assembled disc parts. One of the disc parts is, in a surface to be facing and abutting the other disc part, formed with a circumferential channel and two radial feeding channels between a central hole and the circumferential channel. Moreover, small diameter holes are formed through the disc part between the circumferential channel and the periphery of the disc. By a gear milling cutter formed in this way it is possible to feed flushing fluid from a shaft, extending through the central hole, via the feeding channels, the circumferential channel and the small diameter holes to the cutting inserts at the periphery of the disc. However, such a milling disc will be rather expensive to manufacture due to its two-part form and it would not be possible to form a slot milling tool including a single disc in this way. Also, it is not in practice possible to manufacture a thin slot milling cutter having flushing fluid channels and a thickness of only about 2-10 mm in a two-part form. Moreover, arranging the fluid feeding to the disc from a central shaft to an inner edge surface of the disc is difficult to achieve without leakage and require some type of additional sealing since there always has to be a small but clear play between a mounting shaft and a mounting hole for tolerance reasons.
WO 94/09937 discloses in FIGS. 17 and 18 a rotary ring cutter, which is connected to a fluid flushing system to feed flushing fluid to the cutting edges of the rotary ring cutter. In this embodiment, the rotary ring cutter is mounted onto a head, which in its turn is mounted to a spindle. The flushing fluid is fed through axially directed pipes inside the spindle to an annual distribution chamber inside the head and through radially directed feeding pipes to curved grooves in the surface of the head facing the rotary ring cutter. By means of axially directed passages through the rotary ring cutter, the flushing fluid can be fed to the area of the cutting edges. However, a fluid flushing system according to this document could not be applied to a disc shaped slot milling cutter according to the present disclosure where the cutting edges are arranged along a periphery surface of the disc.
DE 10145006 discloses a slot milling disc having an integrated disc shaped portion and a hub formed portion, which is arranged at the center of the disc shaped portion and which is arranged to be connected to a rotatable shaft at a bearing surface having a recess or spline at the rear end of the hub portion. Around the periphery of the disc shaped portion there are a number of cutting inserts arranged, which are exchangeable by means of screws. In one embodiment the slot milling disc is formed with cooling medium channels extending in an axially direction from a bottom of a recess in the rear end of the hub portion. At a position where the axially cooling medium channels reach the same plane as the disc shaped portion, they change direction by turning ninety degrees and proceed to extend radially within the disc shaped portion and opens eventually into outlet openings in the outer periphery of the disc shaped portion. By a slot milling disc formed in this way, the cooling medium can be fed from the milling machine, through the hub portion, as well as the disc portion and be discharged from its periphery where the cutting and milling operation is performed. However, a slot milling disc designed in this way, having a disc portion and a hub portion, as well as internal cooling medium channels, will be complicated and hence expensive to manufacture. This design will further complicate matters when mounting the slot milling disc to the rotatable shaft of the milling machine, because it will require a sealing arrangement at the connection between the rotatable shaft of the milling machine and the bearing surface at the rear end of the hub portion.
As previously mentioned it is also known to form slot milling discs as thin discs, which do not include the above mentioned hub-portion, such having a thickness of only about 2-10 mm, which around their outer peripheries are provided with a number of cutting edges and which are primarily used for cutting grooves in various work pieces. On one side surfaces they have a bearing surface closest to their center axes, which is adapted to be facing and clamped towards a mounting surface in an end of a rotatable mounting shaft. Flushing of such milling discs with a flushing fluid for purpose of cooling, lubricating and/or flushing away chips, are thereby typically performed by means of one or more flushing fluid jets directed towards the milling disc and the work piece from the outside. However, such cooling, lubricating and/or flushing action arranged on the outside of the milling disc is ineffective, in particular in deep slotting, because the outside jet in general can't reach the relative deep parts of such slots during the slot milling operation.